The Application Of Nanostructured Materials And Enzyme For The Construction Of Electrochemical Bisensors

Researchers pay more and more attention to nano-materials in the study of electrochemical biosensors. With unique small size effect, surface effect, quantum size effect, macroscopic quantum tunneling effect, nanostructured materials are attractive in the developement of biosensors due to their novel optical, electrical, electrocatalytic and biocompatible properties. The performance of the resulting biosensors could be greatly improved with the application of nanomaterials. The details are described as follows:CNTs represent a new kind of promising carbon material over the past years owing to the unique electrical properties such as high surface-to-volume ratio, high chemical stability and a fast electron-transfer rate. With the introduction of Palladium nano-particles, the CNTs/Pd particle multilayer film system showed synergy between CNTs and Pd particle with the significant improvement of redox activity due to the excellent electron-transfer ability of CNTs and Pd particle. The CNTs/Pd particle modified glassy carbon electrode allowed low potential detection of hydrogen peroxide with high sensitivity and fast response time. The biosensor exhibited a wide linear response to hydrogen peroxide ranging from 1×10-7 M to 5×10-2 M with a high sensitivity, the limit of detection was down to 0.5×10-8 M (S/N=3)(in chapter 2).A Ni nanowire arrays where first synthesized by electrodeposition in nanopore polycarbonate (PC) membrane has been developed for the detection of glucose. The size-controlled and uniform Ni nanowire arrays were examined by transmission electron microscope (TEM) and scanning electron microscopy (SEM). The Ni nanowire arrays electrode exhibited a highly electrochemical activity for electrocatalytic oxidation of glucose at +0.55 V in 0.1 M NaOH solution. The Ni nanowire arrays nonenzymatic electrode had more advantages than enzymatic biosensor such as long-term stability. A high sensitivity of 1043μA mM?1 cm?2, a low detection limit of 0.1μM (based on S/N = 3) and rapid response time(<10s). The proposed NiNWA electrode allowed highly sensitive, stable, and fast amperometric sensing of glucose. In addition, interference from the oxidation of common interfering species, such as ascorbic acid and uric acid, were effectively avoided (in chapter 3).A novel tyrosinase electrochemical Bisensor based on hydroxyapatite nanoparticles-chitosan nanocomposite has been developed for the detection of phenolic compounds. The size-controlled and uniform hydroxyapatite nanoparticles were characterized by Scanning electron microscopy (SEM). Tyrosinase was immobilized onto the hydroxyapatite nanoparticles-chitosan nanocomposite matrix-modifed Au electrode. Cyclic voltammetry and electrochemical impedance spectroscopy were used to characterize the tyrosinase electrochemical biosensors. The prepared tyrosinase electrochemical biosensor was used to determine phenolic compounds by the amperometric method at -0.2V. Moreover, the effects of temperature, applied potential and pH on the tyrosinase electrochemical biosensor performance had been studied. A high sensitivity of 2.11×10³μA mM^-1cm^-2 and a rapid response time(<8s), with the limit of detection down to 5×10-9 M (S/N = 3). The Michaelis-Menten constants of the Tyrosinase electrochemical biosensor were estimated to be 3.52, 3.16 and 1.31μM for m-cresol, catechol and phenol respectively. Furthermore, the biosensor exhibited long-term stability, excellent reproducibility and the recovery of tyrosinase biosensor was evaluated with satisfactory results (in chapter 4).